Calculation method for terrain clearance of lowest scattering point of troposphere

Abstract

The invention provides a calculation method for the terrain clearance of the lowest scattering point of the troposphere, and provides a calculation process and method for the terrain clearance of the lowest scattering point of the troposphere by constructing a geometric relationship based on a troposphere scattering path through a transmitting antenna, a receiving antenna, a receiving radio wave ray and a geodetic coordinate of the transmitted radio wave ray encountering a highest obstacle. The geoid well reflects the shape of the earth, the distance between the surfaces of the earth can be accurately measured, compared with a method given by an ITU-R.P.617 proposal, the method better meets the signal transmission loss requirement of the troposphere scattering system, and in troposphere scattering loss prediction, the method has the advantages that the method is simple and convenient to operate, and the cost is low. The calculation accuracy of parameters such as a scatterer dependency coefficient and a loss probability conversion factor can be improved.

Description

Technical Field

[0001] This invention relates to the field of tropospheric calculation, and in particular to a method for calculating altitude. Background Technology

[0002] Based on the method for predicting tropospheric scattering transmission loss proposed by Academician Zhang Minggao, the International Telecommunication Union (ITU) published ITU-RP 617-1, "Propagation Prediction Techniques and Data Required for the Design of Trans-Horizon Radio-Relay Systems," in 1992. In 2012, the formulas for climate zone maps and probability loss fitting were improved, leading to ITU-RP 617-2. In 2013, the prediction of the median average transmission loss distribution for the worst months with a time percentage exceeding 50% was revised, leading to ITU-RP 617-3. In 2017, the formula for calculating the median annual average loss of tropospheric scattering transmission was further modified, and a formula for calculating meteorological factors, as well as a global average sea-level refractive index and refractive index gradient distribution map, were added, leading to ITU-RP 617-4. In 2019, a formula for calculating the minimum scattering point altitude was given, leading to ITU-RP 617-5.

[0003] The altitude of the lowest tropospheric scattering point is an important parameter for calculating the tropospheric scatterer dependence coefficient and the median annual average loss of tropospheric scattering transmission. ITU-RP 617-1, ITU-RP 617-2, ITU-RP 617-3, and ITU-RP 617-4 recommendations provide the following formulas for calculating the altitude of the lowest tropospheric scattering point:

[0004] (km) (1)

[0005] in: The scattering angle is (mrad).

[0006] The equivalent Earth radius factor;

[0007] The radius is the Earth's radius.

[0008] The ITU-RP 617-5 recommendation, after revising the formulas of ITU-RP 617-1 / 2 / 3 / 4, provides the following formula for calculating the altitude of the lowest tropospheric scattering point:

[0009] (2)

[0010] in:

[0011] , These are the altitudes of the transmitting and receiving antennas, respectively.

[0012] The path length of the transmit and receive antennas;

[0013] The scattering angle;

[0014] , These are the line-of-sight elevation angles of the transmitting and receiving antennas, respectively.

[0015] The formulas for calculating the altitude of the lowest tropospheric scattering point in ITU-RP617-1, ITU-RP617-2, ITU-RP617-3, and ITU-RP617-4 are based on the following assumptions.

[0016] 1) Altitude of transmitting antenna Altitude of receiving antenna ;

[0017] 2) The altitude at which the emitted radio waves encounter the highest obstacle. The highest obstacle encountered when receiving radio waves is at altitude. ;

[0018] 3) The straight-line distance between the transmitting antenna and the receiving antenna is equal to the length of their great circle arc;

[0019] 4) Using the equivalent Earth radius length ( The Earth is approximated as a standard sphere.

[0020] Although ITU-RP617-5 revised the calculation method, it is still based on a sphere with an equivalent Earth radius.

[0021] Due to various assumptions, the calculation of the lowest tropospheric scattering point's altitude above the ground can be biased. To accurately predict tropospheric loss, a method for calculating the lowest tropospheric scattering point's altitude above the ground is proposed, based on the transmitting and receiving antennas and the geodetic coordinates of the highest obstacle encountered. Summary of the Invention

[0022] To overcome the shortcomings of existing technologies, this invention provides a method for calculating the altitude of the lowest scattering point in the troposphere above the ground.

[0023] The technical solution adopted by this invention to solve its technical problem is:

[0024] The present invention uses the following methods and steps to calculate the altitude of the lowest scattering point in the troposphere above the ground.

[0025] Step 1. Construct the geometric relationship of the tropospheric scattering path;

[0026] The geometric relationship of the tropospheric scattering path is as follows Figure 1 As shown.

[0027] in: The geodetic coordinates of the transmitting antenna; The geodetic coordinates of the receiving antenna; The coordinates of the highest obstacle encountered when the emitted radio wave rays are emitted; The coordinates of the highest obstacle encountered when receiving radio waves; This is the lowest scattering point; The lowest scattering point With the center of the Earth The intersection of the line and the Earth's surface; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna; The distance between the highest obstacle encountered when receiving radio waves and the receiving antenna; Minimum scattering angle; The angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight; The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight;

[0028] Step 2. Calculate the transmitting antenna With receiving antenna straight-line distance between ;

[0029] Step 3. Calculate the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna. ;

[0030] Step 4. Calculate the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. :

[0031] (7)

[0032] in: The radius of the Earth; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna.

[0033] Step 5. Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. ;

[0034] Step 6. Calculate the angle between the line connecting the transmitting and receiving antennas and the receiving horizon. ;

[0035] (10)

[0036] in: The radius of the Earth; The distance between the highest obstacle encountered and the receiving antenna when receiving radio waves.

[0037] Step 7. Calculate the distance between the transmitting antenna and the Earth's center. ;

[0038] (11)

[0039] Step 8. Calculate the distance between the receiving antenna and the center of the Earth. ;

[0040] (12)

[0041] Step 9. Calculate the transmit antenna-receive antenna connection. Connecting the transmitting antenna to the center of the sphere The included angle :

[0042] (13)

[0043] Step 10. Calculate the transmit antenna-receive antenna connection. Connection with the receiving antenna-center The included angle :

[0044] (14)

[0045] Step 11. Calculate the great circle lengths of the transmitting and receiving antennas. :

[0046] (15)

[0047] Step 12. Calculate the height of the lowest tropospheric scattering point above the ground. ;

[0048] Depend on Figure 1 It can be seen that, The length of this is the height of the lowest scattering point in the troposphere above the ground.

[0049] set up:

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Let the variable (16)

[0056] The lowest scattering point in the troposphere is at the following altitude:

[0057] (17)

[0058] This represents the lowest scattering point in the troposphere above the ground.

[0059] Step 2 calculates the transmitting antenna. With receiving antenna straight-line distance between The specific steps are as follows:

[0060] Step 2.1: Convert the positions of the transmitting and receiving antennas to WGS-84 geocentric rectangular coordinates;

[0061] The geocentric rectangular coordinates of the transmitting antenna WGS-84 are:

[0062] (2)

[0063] in: Longitude of the transmitting antenna The latitude of the transmitting antenna. The altitude of the transmitting antenna. For the first eccentricity, , The semi-major axis of the Earth's ellipsoid. ;

[0064] The geocentric rectangular coordinates of the receiving antenna WGS-84 are:

[0065] (3)

[0066] in: Longitude of the receiving antenna; Latitude of the receiving antenna; Altitude of the receiving antenna; For the first eccentricity, ; The major radius of the Earth's reference ellipsoid;

[0067] Step 2.2: Calculate the straight-line distance between the transmitting antenna and the receiving antenna:

[0068] (4)

[0069] The specific steps for calculating the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna in step 3 are as follows:

[0070] The location of the emitted radio wave ray encountering the highest obstacle, converted to WGS-84 geocentric rectangular coordinates, is:

[0071] (5)

[0072] in: The longitude of the highest obstacle encountered when emitting radio waves; The latitude at which the emitted radio waves encounter the highest obstacle. The altitude of the highest obstacle encountered when emitting radio waves.

[0073] Calculate the distance between the transmitted radio wave beam encountering the highest obstacle and the transmitting antenna:

[0074] (6).

[0075] Step 5 calculates the distance between the received radio wave beam encountering the highest obstacle and the receiving antenna. The specific steps are as follows:

[0076] The received radio waves are converted to WGS-84 Earth-centered, Earth-fixed rectangular coordinates upon encountering the highest obstacle.

[0077] (8)

[0078] in: The longitude of the highest obstacle encountered when receiving radio waves; The latitude at which the highest obstacle is encountered in order to receive radio waves; The altitude of the highest obstacle encountered in order to receive radio waves;

[0079] Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna.

[0080] (9).

[0081] An electronic device includes: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs are configured to perform the methods described above.

[0082] A computer-readable storage medium storing program code that can be invoked by a processor to perform the method described above.

[0083] The beneficial effects of this invention are that the geoid accurately reflects the shape of the Earth and can accurately measure distances between Earth's surfaces. This invention constructs a calculation process and method for the altitude of the lowest tropospheric scattering point based on the geometric relationship of the tropospheric scattering path by using a transmitting antenna, a receiving antenna, the received radio waves, and the geodetic coordinates of the highest obstacle encountered by the transmitted radio waves. Compared with the method given in ITU-RP 617 Recommendation, this invention is more in line with the signal transmission loss requirements of tropospheric scattering systems and can improve the calculation accuracy of parameters such as the scatterer dependence coefficient and the loss probability conversion factor in tropospheric scattering loss prediction. Attached Figure Description

[0084] Figure 1 This is a schematic diagram of the geometric relationship of the tropospheric scattering path in this invention.

[0085] Figure 2 shows the difference in altitude between the lowest tropospheric scattering point and the ground level in accordance with the present invention and ITU-RP617-1 / 2 / 3 / 4. The analysis results are shown in Figure 2(a), which shows the analysis results when the transmitting antenna is 10km high; Figure 2(b), which shows the analysis results when the transmitting antenna is 5km high; and Figure 2(c), which shows the analysis results when the transmitting antenna is 1km high.

[0086] Figure 3 shows the difference in altitude between the lowest tropospheric scattering point and the ground level according to the present invention and ITU-RP617-5. The analysis results are shown in Figure 3(a), which shows the analysis results when the transmitting antenna height is 10km, Figure 3(b), which shows the analysis results when the transmitting antenna height is 5km, and Figure 3(c), which shows the analysis results when the transmitting antenna height is 1km. Detailed Implementation

[0087] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0088] Step 1. Construct the geometric relationship of the tropospheric scattering path;

[0089] The geometric relationship of the tropospheric scattering path is as follows Figure 1 As shown.

[0090] in: The geodetic coordinates of the transmitting antenna; The geodetic coordinates of the receiving antenna; The coordinates of the highest obstacle encountered when the emitted radio wave rays are emitted; The coordinates of the highest obstacle encountered when receiving radio waves; This is the lowest scattering point; The lowest scattering point With the center of the Earth The intersection of the line and the Earth's surface; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna; The distance between the highest obstacle encountered when receiving radio waves and the receiving antenna; Minimum scattering angle; The angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight; The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight;

[0091] Step 2. Calculate the transmitting antenna With receiving antenna straight-line distance between ;

[0092] Step 2.1: Convert the positions of the transmitting and receiving antennas to WGS-84 geocentric rectangular coordinates;

[0093] The geocentric rectangular coordinates of the transmitting antenna WGS-84 are:

[0094] (2)

[0095] in: Longitude of the transmitting antenna The latitude of the transmitting antenna. The altitude of the transmitting antenna. For the first eccentricity, , The semi-major axis of the Earth's ellipsoid. ;

[0096] The geocentric rectangular coordinates of the receiving antenna WGS-84 are:

[0097] (3)

[0098] in: Longitude of the receiving antenna; Latitude of the receiving antenna; Altitude of the receiving antenna; For the first eccentricity, ; The major radius of the Earth's reference ellipsoid;

[0099] Step 2.2: Calculate the straight-line distance between the transmitting antenna and the receiving antenna:

[0100] (4)

[0101] Step 3. Calculate the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna. ;

[0102] The location of the emitted radio wave ray encountering the highest obstacle, converted to WGS-84 geocentric rectangular coordinates, is:

[0103] (5)

[0104] in: The longitude of the highest obstacle encountered when emitting radio waves; The latitude at which the emitted radio waves encounter the highest obstacle. The altitude of the highest obstacle encountered when emitting radio waves;

[0105] Calculate the distance between the transmitted radio wave beam encountering the highest obstacle and the transmitting antenna:

[0106] (6)

[0107] Step 4. Calculate the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. :

[0108] (7)

[0109] in: The radius of the Earth;

[0110] The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna.

[0111] Step 5. Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. ;

[0112] The received radio waves are converted to WGS-84 Earth-centered, Earth-fixed rectangular coordinates upon encountering the highest obstacle.

[0113] (8)

[0114] in: The longitude of the highest obstacle encountered when receiving radio waves; The latitude at which the highest obstacle is encountered in order to receive radio waves; The altitude of the highest obstacle encountered in order to receive radio waves;

[0115] Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna.

[0116] (9)

[0117] Step 6. Calculate the angle between the line connecting the transmitting and receiving antennas and the receiving horizon. ;

[0118] (10)

[0119] in: The radius of the Earth; The distance between the highest obstacle encountered and the receiving antenna when receiving radio waves.

[0120] Step 7. Calculate the distance between the transmitting antenna and the Earth's center. ;

[0121] (11)

[0122] Step 8. Calculate the distance between the receiving antenna and the center of the Earth. ;

[0123] (12)

[0124] Step 9. Calculate the transmit antenna-receive antenna connection. Connecting the transmitting antenna to the center of the sphere The included angle :

[0125] (13)

[0126] Step 10. Calculate the transmit antenna-receive antenna connection. Connection with the receiving antenna-center The included angle :

[0127] (14)

[0128] Step 11. Calculate the great circle lengths of the transmitting and receiving antennas. :

[0129] (15)

[0130] Step 12. Calculate the height of the lowest tropospheric scattering point above the ground. ;

[0131] Depend on Figure 1 It can be seen that, The length of this is the height of the lowest scattering point in the troposphere above the ground.

[0132] set up:

[0133]

[0134]

[0135]

[0136]

[0137]

[0138] Let the variable (16)

[0139] The lowest scattering point in the troposphere is at the following altitude:

[0140] (17)

[0141] This represents the lowest scattering point in the troposphere above the ground.

[0142] The following is an example:

[0143] 1) Antenna location

[0144] Longitude of the transmitting antenna ;latitude The altitudes are respectively , , .

[0145] Altitude of receiving antenna .

[0146] 2) Scope of Analysis

[0147] Assuming the Earth is a standard reference ellipsoid, the distance beyond line of sight can be calculated by applying equation (18) based on the altitude of the transmitting and receiving antennas.

[0148] (18)

[0149] Table 1. Beyond-line-of-sight distances at different antenna altitudes

[0150]

[0151] When the distance between the receiving antenna and the transmitting antenna is greater than the beyond-line-of-sight distance (As shown in Table 1), in the region of 28°–40°N latitude and 100°–118°E longitude, the altitude of the lowest tropospheric scattering point was calculated using the methods provided in this invention and ITU-RP617-1 / 2 / 3 / 4 and ITU-RP617-5 recommendations, respectively. The altitude difference between the two methods was then compared. Perform the analysis.

[0152] Figures 2(a), 2(b), and 2(c) show the height difference above the ground of the lowest tropospheric scattering point according to the present invention and ITU-RP617-1 / 2 / 3 / 4. The analysis results. Within the analysis range, when the altitude of the transmitting antenna... The calculation results of the lowest tropospheric scattering point altitude provided by this invention and the method provided in ITU-RP617-1 / 2 / 3 / 4 differ by more than 2.6 km; the altitude of the transmitting antenna... The calculation results differed by more than 3.5 km; the altitude of the transmitting antenna The calculation results differed by more than 4.8 km.

[0153] Figures 3(a), 3(b), and 3(c) show the height difference above the ground of the lowest tropospheric scattering point according to the present invention and ITU-RP617-5. The analysis results show that, within the analysis range, when the altitude of the transmitting antenna is... The two methods yielded a maximum difference of 36 km in the calculated height from the lowest tropospheric scattering point to the line connecting the transmitting and receiving antennas; the transmitting antenna height... The calculation results differed by more than 35km; the height of the transmitting antenna... The calculation results differed by more than 34 km.

[0154] The results of calculating the altitude of the lowest tropospheric scattering point using the methods provided in this invention and ITU-RP617 differ to some extent. This is mainly because the mathematical model in ITU-RP617 is derived based on a variety of assumptions.

Claims

1. A method for calculating the altitude of the lowest tropospheric scattering point above the ground, characterized in that... Includes the following steps: Step 1. Construct the geometric relationship of the tropospheric scattering path; in: The geodetic coordinates of the transmitting antenna; The geodetic coordinates of the receiving antenna; The coordinates of the highest obstacle encountered when the emitted radio wave rays are emitted; The coordinates of the highest obstacle encountered when receiving radio waves; The lowest scattering point; The lowest scattering point With the center of the Earth The point where the line intersects the Earth's surface; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna; The distance between the highest obstacle encountered when receiving radio waves and the receiving antenna; Minimum scattering angle; The angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight; The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight; Step 2. Calculate the transmitting antenna With receiving antenna straight-line distance between ; Step 3. Calculate the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna. ; Step 4. Calculate the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. : （7） in: The radius of the Earth; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna; Step 5. Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. ; Step 6. Calculate the angle between the line connecting the transmitting and receiving antennas and the receiving horizon. ; （10） in: The radius of the Earth; The distance between the highest obstacle encountered when receiving radio waves and the receiving antenna; Step 7. Calculate the distance between the transmitting antenna and the Earth's center. ; （11） Step 8. Calculate the distance between the receiving antenna and the center of the Earth. ; （12） Step 9. Calculate the transmit antenna-receive antenna connection. Connecting the transmitting antenna to the center of the sphere The included angle : （13） Step 10. Calculate the transmit antenna-receive antenna connection. Connection with the receiving antenna-center The included angle : （14） Step 11. Calculate the great circle lengths of the transmitting and receiving antennas. : （15） Step 12. Calculate the height of the lowest tropospheric scattering point above the ground. ; The length of this is the height of the lowest scattering point in the troposphere above the ground. set up: ; ； ； ； ； ； Let the variable (16); The lowest scattering point in the troposphere is at the following altitude: （17）； This represents the lowest scattering point in the troposphere above the ground.

2. The method for calculating the altitude of the lowest tropospheric scattering point above the ground according to claim 1, characterized in that: Step 2 calculates the transmitting antenna. With receiving antenna straight-line distance between The specific steps are as follows: Step 2.1: Convert the positions of the transmitting and receiving antennas to WGS-84 geocentric rectangular coordinates; The geocentric rectangular coordinates of the transmitting antenna WGS-84 are: （2） in: Longitude of the transmitting antenna The latitude of the transmitting antenna. The altitude of the transmitting antenna. For the first eccentricity, , The semi-major axis of the Earth's ellipsoid. ; The geocentric rectangular coordinates of the receiving antenna WGS-84 are: （3） in: Longitude of the receiving antenna; Latitude of the receiving antenna; Altitude of the receiving antenna; For the first eccentricity, ; The major radius of the Earth's reference ellipsoid; ; Step 2.2: Calculate the straight-line distance between the transmitting antenna and the receiving antenna: （4）。 3. The method for calculating the altitude of the lowest tropospheric scattering point above the ground according to claim 1, characterized in that: The specific steps for calculating the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna in step 3 are as follows: The location of the emitted radio wave ray encountering the highest obstacle, converted to WGS-84 geocentric rectangular coordinates, is: （5） in: The longitude of the highest obstacle encountered when emitting radio waves; The latitude at which the emitted radio waves encounter the highest obstacle. The altitude of the highest obstacle encountered when emitting radio waves; Calculate the distance between the transmitted radio wave beam encountering the highest obstacle and the transmitting antenna: （6）。 4. The method for calculating the altitude of the lowest tropospheric scattering point above the ground according to claim 1, characterized in that: Step 5 calculates the distance between the received radio wave beam encountering the highest obstacle and the receiving antenna. The specific steps are as follows: The received radio waves are converted to WGS-84 Earth-centered, Earth-fixed rectangular coordinates upon encountering the highest obstacle. （8） in: The longitude of the highest obstacle encountered when receiving radio waves; The latitude at which the highest obstacle is encountered in order to receive radio waves; The altitude of the highest obstacle encountered in order to receive radio waves; Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. （9）。 5. An electronic device, characterized in that, include: One or more processors; Memory; One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs being configured to perform the method as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores program code that can be invoked by a processor to execute the method as described in any one of claims 1-4.

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